Kirk mentions in "Conscience of the King" that they dim the lights on the Enterprise at night to simulate Earth conditions, but I'm not sure if we ever actually saw this done.

Dim as in what was done in TNG, with the obviousness of a sunset and sunrise in a few seconds on command? No, I don't recall that happening.

However, there were plenty of times when the lights seemed dim out in the corridors. Also, there were plenty of times when the lighting was under those wonky color filters, which often seemed low-intensity. But, because I'm not literal-minded (and because the camera went all fuzzy on the beautiful female guest stars), I can't tell if the lighting aboard the TOS Enterprise was supposed to be literally multicolored like that, or if it was all kind of poetic license for the purpose of composing interesting pictures on our TV's.

__________________“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)